It seems a surprising suggestion. Can it be true that what we put on our dinner plates could have an effect on global warming? It appears so. A new report is to warn the livestock industry generates 8 per cent of all UK greenhouse gas emissions - but that eating some meat is good for the planet. It will also say organic farming may be no better than intensive methods for reducing emissions, though organic practices have other advantages.

The report, which aims to be the most comprehensive study of the subject yet completed, claims a vegetarian diet including cheese, butter and milk would probably not noticeably reduce carbon emissions because dairy cows are a major source of the biggest greenhouse gas pollution from livestock - the methane released when cattle burp.

A vegan diet would be better, but it would ignore some benefits of rearing grazing animals, said Tara Garnett, from the Food Climate Research Network at Surrey University, who wrote the report. 'A little bit of livestock production is probably a good thing for the environment,' she said. 'Livestock provide a very important service in terms of maintaining landscape and soil quality and maintaining biodiversity: you get different animals grazing at different levels and if you didn't have them you'd have a very different landscape.'

Garnett said further research was needed to work out how much less meat should be eaten, but the report suggested it would be 'considerably less'. Next year Compassion in World Farming, an animal welfare group, will launch a fresh campaign urging people to eat less meat.

The growing environmental concerns about meat come at a time of rising health worries: as well as warnings of an epidemic of obesity, the World Cancer Research Fund recently said eating red meat even in small quantities can increase the risk of several cancers.

'All the different strands are building up: lots more information on diet, lots more information on livestock production, and the climate statistics... so we're making a strong case for reducing meat production and consumption,' said Joyce D'Silva, Compassion's ambassador.

Britons eat an average of 82g of protein a day, of which about 50g is from meat - equivalent to a chicken breast and a lamb chop. The figure is relatively low for a developed country, but higher than developing nations and 25-50 per cent above the World Health Organisation recommendation. This adds up, for the UK, to a total of more than 1m tonnes of beef, 1.3m tonnes of pork and bacon, 1.8m tonnes of poultry, nearly 400,000 tonnes of lamb and mutton, plus 13m tonnes of milk, cheese and other dairy products eaten every year.

Vegetarians and some environmentalists have warned for years about the environmental benefits of eating less or no meat, but as incomes have grown the average Briton eats 50 per cent more meat than four decades ago and global consumption is forecast to double by 2050, says Compassion.

Earlier this year, the Vegetarian Society claimed livestock generate nearly one fifth of global greenhouse gas emissions, more than transport. However, there is disagreement on the benefits of giving up meat: the figures, measured in 'carbon dioxide equivalent' to allow comparison of different greenhouse gases, range from a difference of 0.4 tonnes between a diet high in meat and vegetarian diets, to several times that figure, said Dave Hampton, a carbon reduction expert.

The Food Climate Research Centre report claims to study the subject more comprehensively by including full 'life cycle' analysis of meat production, from the fertiliser for feed to transport from the farm, and the carbon 'cost' of producing alternatives to meat and other animal products like leather and wool.

Garnett concludes that to reduce carbon emissions consumers need to eat less, but changes can also be made to production. Emissions from organic farming were 'unlikely to differ much' from intensive farming. Instead, the report recommends 'marginal livestock rearing', which would see animals grazed only on land which could not be used for other purposes, but warns meat prices would have to rise to help support farmers and the rural economy.

The Meat and Livestock Commission said there could be other ways to reduce the carbon footprint of meat eating, including using more UK-produced food which did not have to be transported as far and changing the diet of cows, which could reduce methane output by half.

The Vegetarian Society said it wanted to draw attention to the benefits of eating less meat, but it also recommended people chose seasonal, local and organic products to have the biggest impact.

The Soil Association, which represents the organic industry, disputed the idea it was not more climate-friendly, saying that a study for Defra showed organic production led to a 26 per cent reduction in carbon emissions from agriculture.

To help consumers wade through the confusing advice, Hampton says people who want to reduce emissions should first buy local food that does not need to be transported and choose organic produce and reduce meat and dairy foods.

'A person switching from highest to lowest impact for a year can save 1-2 tonnes of carbon dioxide equivalent - the same annual saving as conserving £300 worth of gas on heating, [or] cutting down 5,000 miles a year in an average car, [or] avoiding one return flight to Europe,' he added.

Eating less meat alone would not be enough for many people, warned Hampton: 'For a well-off professional with above average disposable income, no amount of vegetarian or vegan eating, recycling, organic local produce or packaging avoidance will make any shrinkage of our shadow. Flying time, petrol spend and energy bills will predominate.'